Fix jerky behavior when live resizing an OS window on platforms that report live resize being and end events

Also disable live resize begin/end events on Wayland since they are not
reliable.

On platforms that support live resize begin/end use a separately
configurable pause time before the screen is redrawn.

Fixes #6341

glfw/wl_window.c

@@ -504,6 +504,12 @@ _glfwPlatformToggleFullscreen(_GLFWwindow *window, unsigned int flags UNUSED) {
     return !already_fullscreen;
 }
 
+static void
+report_live_resize(_GLFWwindow *w, bool started) {
+    // disabled as mutter, for instance, does not send a configure event when the user stops resizing (aka releases the mouse button)
+    if (false) _glfwInputLiveResize(w, started);
+}
+
 static void
 xdgToplevelHandleConfigure(void* data,
                                        struct xdg_toplevel* toplevel UNUSED,
@@ -536,7 +542,7 @@ xdgToplevelHandleConfigure(void* data,
     if (new_states & TOPLEVEL_STATE_RESIZING) {
         if (width) window->wl.user_requested_content_size.width = width;
         if (height) window->wl.user_requested_content_size.height = height;
-        if (!(window->wl.current.toplevel_states & TOPLEVEL_STATE_RESIZING)) _glfwInputLiveResize(window, true);
+        if (!(window->wl.current.toplevel_states & TOPLEVEL_STATE_RESIZING)) report_live_resize(window, true);
     }
     if (width != 0 && height != 0)
     {
@@ -606,7 +612,7 @@ static void xdgSurfaceHandleConfigure(void* data,
             window->wl.current.width = width;
             window->wl.current.height = height;
             _glfwInputWindowFocus(window, window->wl.current.toplevel_states & TOPLEVEL_STATE_ACTIVATED);
-            if (live_resize_done) _glfwInputLiveResize(window, false);
+            if (live_resize_done) report_live_resize(window, false);
         }
     }
 

kitty/child-monitor.c

@@ -1004,9 +1004,19 @@ process_pending_resizes(monotonic_t now) {
         if (w->live_resize.in_progress) {
             bool update_viewport = false;
             if (w->live_resize.from_os_notification) {
-                if (w->live_resize.os_says_resize_complete || (now - w->live_resize.last_resize_event_at) > 1) update_viewport = true;
+                if (w->live_resize.os_says_resize_complete) update_viewport = true;
+                else {
+                    // prevent a "hang" if the OS never sends a resize complete event
+                    // also reflow the screen when the user pauses resizing so the user can see what the resized
+                    // screen will look like.
+                    if ((now - w->live_resize.last_resize_event_at) > OPT(resize_debounce_time).on_pause) update_viewport = true;
+                    else {
+                        global_state.has_pending_resizes = true;
+                        set_maximum_wait(s_double_to_monotonic_t(0.05));
+                    }
+                }
             } else {
-                monotonic_t debounce_time = OPT(resize_debounce_time);
+                monotonic_t debounce_time = OPT(resize_debounce_time).on_end;
                 // if more than one resize event has occurred, wait at least 0.2 secs
                 // before repainting, to avoid rapid transitions between the cells banner
                 // and the normal screen

kitty/options/definition.py

@@ -1065,12 +1065,18 @@ faded and one being fully opaque.
     )
 
 
-opt('resize_debounce_time', '0.1',
-    option_type='positive_float', ctype='time',
+opt('resize_debounce_time', '0.1 0.5',
+    option_type='resize_debounce_time', ctype='!resize_debounce_time',
     long_text='''
-The time to wait before redrawing the screen when a resize event is received (in
-seconds). On platforms such as macOS, where the operating system sends events
-corresponding to the start and end of a resize, this number is ignored.
+The time to wait before redrawing the screen during a live resize of the OS
+window, when no new resize events have been received, i.e. when resizing is
+either paused or finished. On platforms such as macOS, where the operating
+system sends events corresponding to the start and end of a live resize, the
+second number is used for redraw-after-pause since kitty can distinguish
+between a pause and end of resizing.  On such systems the first number is
+ignored and redraw is immediate after end of resize.  On other systems the
+first number is used so that kitty is "ready" quickly after the end of
+resizing, while not also continuously redrawing, to save energy.
 '''
     )
 

kitty/options/parse.py

@@ -13,12 +13,12 @@ from kitty.options.utils import (
     deprecated_hide_window_decorations_aliases, deprecated_macos_show_window_title_in_menubar_alias,
     deprecated_send_text, disable_ligatures, edge_width, env, font_features, hide_window_decorations,
     macos_option_as_alt, macos_titlebar_color, modify_font, narrow_symbols, optional_edge_width,
-    parse_map, parse_mouse_map, paste_actions, remote_control_password, resize_draw_strategy,
-    scrollback_lines, scrollback_pager_history_size, shell_integration, store_multiple, symbol_map,
-    tab_activity_symbol, tab_bar_edge, tab_bar_margin_height, tab_bar_min_tabs, tab_fade,
-    tab_font_style, tab_separator, tab_title_template, titlebar_color, to_cursor_shape, to_font_size,
-    to_layout_names, to_modifiers, url_prefixes, url_style, visual_window_select_characters,
-    window_border_width, window_size
+    parse_map, parse_mouse_map, paste_actions, remote_control_password, resize_debounce_time,
+    resize_draw_strategy, scrollback_lines, scrollback_pager_history_size, shell_integration,
+    store_multiple, symbol_map, tab_activity_symbol, tab_bar_edge, tab_bar_margin_height,
+    tab_bar_min_tabs, tab_fade, tab_font_style, tab_separator, tab_title_template, titlebar_color,
+    to_cursor_shape, to_font_size, to_layout_names, to_modifiers, url_prefixes, url_style,
+    visual_window_select_characters, window_border_width, window_size
 )
 
 
@@ -1151,7 +1151,7 @@ class Parser:
         ans['repaint_delay'] = positive_int(val)
 
     def resize_debounce_time(self, val: str, ans: typing.Dict[str, typing.Any]) -> None:
-        ans['resize_debounce_time'] = positive_float(val)
+        ans['resize_debounce_time'] = resize_debounce_time(val)
 
     def resize_draw_strategy(self, val: str, ans: typing.Dict[str, typing.Any]) -> None:
         ans['resize_draw_strategy'] = resize_draw_strategy(val)

kitty/options/to-c-generated.h

@@ -592,7 +592,7 @@ convert_from_opts_window_logo_alpha(PyObject *py_opts, Options *opts) {
 
 static void
 convert_from_python_resize_debounce_time(PyObject *val, Options *opts) {
-    opts->resize_debounce_time = parse_s_double_to_monotonic_t(val);
+    resize_debounce_time(val, opts);
 }
 
 static void

kitty/options/to-c.h

@@ -255,3 +255,9 @@ tab_bar_margin_height(PyObject *val, Options *opts) {
     opts->tab_bar_margin_height.outer = PyFloat_AsDouble(PyTuple_GET_ITEM(val, 0));
     opts->tab_bar_margin_height.inner = PyFloat_AsDouble(PyTuple_GET_ITEM(val, 1));
 }
+
+static void
+resize_debounce_time(PyObject *src, Options *opts) {
+    opts->resize_debounce_time.on_end = s_double_to_monotonic_t(PyFloat_AsDouble(PyTuple_GET_ITEM(src, 0)));
+    opts->resize_debounce_time.on_pause = s_double_to_monotonic_t(PyFloat_AsDouble(PyTuple_GET_ITEM(src, 1)));
+}

kitty/options/types.py

@@ -564,7 +564,7 @@ class Options:
     pointer_shape_when_grabbed: choices_for_pointer_shape_when_grabbed = 'arrow'
     remember_window_size: bool = True
     repaint_delay: int = 10
-    resize_debounce_time: float = 0.1
+    resize_debounce_time: typing.Tuple[float, float] = (0.1, 0.5)
     resize_draw_strategy: int = 0
     resize_in_steps: bool = False
     scrollback_fill_enlarged_window: bool = False

kitty/options/utils.py

@@ -604,6 +604,13 @@ def resize_draw_strategy(x: str) -> int:
     return cmap.get(x.lower(), 0)
 
 
+def resize_debounce_time(x: str) -> Tuple[float, float]:
+    parts = x.split(maxsplit=1)
+    if len(parts) == 1:
+        return positive_float(parts[0]), 0.5
+    return positive_float(parts[0]), positive_float(parts[1])
+
+
 def visual_window_select_characters(x: str) -> str:
     import string
     valid_characters = string.digits + string.ascii_uppercase

kitty/state.h

@@ -70,7 +70,7 @@ typedef struct {
     bool window_alert_on_bell;
     bool debug_keyboard;
     bool allow_hyperlinks;
-    monotonic_t resize_debounce_time;
+    struct { monotonic_t on_end, on_pause; } resize_debounce_time;
     MouseShape pointer_shape_when_grabbed;
     MouseShape default_pointer_shape;
     MouseShape pointer_shape_when_dragging;